Fritz R. Fiedler

A numerical method for simulating discontinuous shallow flow over an infiltrating surface

SUMMARY A numerical method based on the MacCormack finite difference scheme is presented. The method was developed for simulating two-dimensional overland flow with spatially variable infiltration and microtopography using the hydrodynamic flow equations. The basic MacCormack scheme is enhanced by using the method of fractional steps to simplify application; treating the friction slope, a stiff source term, point-implicitly, plus, for numerical oscillation control and stability, upwinding the convective acceleration term. A higher-order smoothing operator is added to aid oscillation control when simulating flow over highly variable surfaces. Infiltration is simulated with the Green‐Ampt model coupled to the surface water component in a manner that allows dynamic interaction. The developed method will also be useful for simulating irrigation, tidal flat and wetland circulation, and floods. Copyright

Managing uncertainty in thermal water quality trading programs

Thermal water quality trading is an emerging policy tool that allows thermal polluters to comply with effluent restrictions by paying nearby landowners to plant shade trees. We created a system dynamics model of a hypothetical thermal trading program and conducted scenario analysis to study how weather, climate, and trading behavior might influence program effectiveness. It is likely that neither thermal trading nor conventional regulation can reduce water temperatures to desired levels, but the model indicates that trading ratios, used to account for uncertainty, lead programs to decrease water temperatures below those produced through conventional regulation.

Simplified Analysis Method for Natural Dispersion of Highway Storm Water Runoff in Rural Areas

Storm water quantity control has long been a challenge for highway designers. Traditionally, centralized best management practice designs are often cost prohibitive and inefficient in many rural highway applications. The use of existing vegetated rights-of-way as a method of treating storm water, a component of the broader storm water treatment concept more generally referred to as low-impact development, has become a primary focus of the Washington State Department of Transportation. To design and use such storm water management controls adequately, however, further research and correlation between numerical infiltrationrunoff models and field experiments were needed. This paper focuses on evaluating natural dispersion performance through the use of simulated rainfall runoff data collected with a field-scale rainfall simulator and a numerical model to study the effects of slope length, angle, and impervious contributory area on natural dispersion applications. A simple new equation was developed to analy...